Tricuspid valve annulus (anatomy)

The tricuspid valve annulus is part of the fibrous skeleton of the heart. It consists of a ring of collagenous tissue that generally extends around the line of attachment of the leaflets of the tricuspid valve. It merges with the fibrous intermediate layer of the leaflets and with other valves via the fibrous skeleton. However, at some points the lamina fibrosa of the leaflets may pass for a distance subendocardially before the annulus is reached - the line of attachment of the valve does not necessarily correspond with the site of the annulus.

The annulus is not uniformly thick throughout its circumference and it is contributed to by several elements:

• the right fibrous trigone where it faces the tricuspid valve
• right and left long, tapering subendocardial fibrous bands - the fila coronaria - passing laterally from the right fibrous trigone
• a very thin layer of connective tissue between the distal ends of the fila coronaria laterally